1. Field of the Invention
This invention relates to a magnetic inductive type thin film magnetic head and more particularly to a thin film magnetic head suitable for use with the so-called azimuth recording system.
2. Description of the Prior Art
In general, a thin film magnetic head has been known as a device for recording information signals with a high density on a magnetic recording medium such as a magnetic tape or a magnetic disk.
The thin film magnetic head is practically used as the magnetic head suitable for high speed high density recording for the following reasons. First, it is high in effective magnetic permeability in the range of higher frequencies through the use of a thin ferromagnetic metal film, such as Fe-Al-Si alloy film, as the magnetic core material, while it has a high saturation magnetic flux density and therefore it is excellent in a recording and reproducing efficiency. In addition, it can be controlled easily as to the gap length so that a narrow gap may be produced. It has a reduced thickness in the vicinity of the magnetic gap so that a recording magnetic field of a steep gradient may be produced. Since a large number cf head elements are formed in a lump on the wafer, a large number of magnetic heads can be mass-produced.
Recently, what is called the azimuth recording system in which the guard bands between the recording tracks are removed for further improving the recording density has been evolved. In this system, the magnetic gap of the magnetic head is arranged obliquely to the widthwise direction of the recording track. What is called the azimuth loss is ingeniously employed in order to prevent the occurrence of the cross-talk phenomenon caused by signal reproduction from the adjacent tracks.
So far, the thin film magnetic head suitable for azimuth recording, that is, the magnetic gap of which is inclined relative to the running direction of the magnetic medium, was prepared by the following method. First, the lower magnetic film is formed on the base or substrate and the coil conductor is wound through an insulating film on the lower magnetic film. The upper magnetic film is formed through the intermediary of a gap spacer or an insulating film to form a magnetic gap. Since the magnetic gap is formed at this stage in parallel with the substrate acting as the reference surface, the heads are produced by slicing the wafer obliquely to the reference surface to afford an azimuth to the magnetic gap.
However, when the heads are produced by slicing the wafer obliquely as described above, the sliced surface needs to be precisely ground in order to assure an azimuth accuracy of the magnetic gap. Hence, the production process of the thin film magnetic head becomes more complex while the satisfactory azimuth accuracy is not always achieved.
Recently, in pursuit for a high picture quality recording in the field of VTRs, there has been evolved what is called a digital VTR in which the video signals are recorded by the pulse code modulation (PCM) system. Since the volume of signals to be recorded is drastically increased in the digital VTR as compared to the conventional or analog VTR, plural tracks need to be recorded simultaneously (multichannel recording system). Hence a demand has been raised for evolving a multi-channel thin film magnetic head having an azimuth in the magnetic gap.
However, in the above described conventional method of producing the multi-channel thin film magnetic head, the azimuth is obtained only at the time of slicing the head block into head pieces, so that it is not possible to produce the multi-channel thin film magnetic heads having the in-line azimuth gaps.
Hence it was necessary in the prior art to have the head chips secured accurately to the head drum after the proper azimuth was set relative to the tape running direction. However, this operation usually required a great deal of skill and, above all, a considerable painstaking operation was required in the adjustment of the gap interval or the setting of the track height. As a result, the efficiency of the assembling operation is markedly lowered, while problems are also involved in the Yield and production costs.